Patents by Inventor David Anthony Freitas

David Anthony Freitas has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6525896
    Abstract: A method and apparatus for high voltage applications, with the latest MOSFET technology having limited terminal-to-terminal voltage capability, includes a switch circuit having at least two serially coupled MOSFETs and a two-stage MOSFET connection using a plurality of resistors, and/or a bipolar transistor, and a plurality of diodes. One of the high voltage applications is a high speed write driver in a computer disk drive. The switch circuit switches on/off between zero volt and a voltage higher than a maximum terminal-to-terminal voltage of a single MOSFET which is typically five volts. A required voltage in high voltage applications can be in excess of, for example, 8 or 9 volts.
    Type: Grant
    Filed: May 14, 1998
    Date of Patent: February 25, 2003
    Assignee: International Business Machines Corporation
    Inventors: Paul Wingshing Chung, David Anthony Freitas, Kevin Roy Vannorsdel
  • Publication number: 20020057512
    Abstract: A method and apparatus for high voltage applications, with the latest MOSFET technology having limited terminal-to-terminal voltage capability, includes a switch circuit having at least two serially coupled MOSFETs and a two-stage MOSFET connection using a plurality of resistors, and/or a bipolar transistor, and a plurality of diodes. One of the high voltage applications is a high speed write driver in a computer disk drive. The switch circuit switches on/off between zero volt and a voltage higher than a maximum terminal-to-terminal voltage of a single MOSFET which is typically five volts. A required voltage in high voltage applications can be in excess of, for example, 8 or 9 volts.
    Type: Application
    Filed: May 14, 1998
    Publication date: May 16, 2002
    Inventors: PAUL WINGSHING CHUNG, DAVID ANTHONY FREITAS, KEVIN ROY VANNORSDEL
  • Patent number: 6356113
    Abstract: A recording channel front-end circuit for driving a write element over a transmission line interconnect provides the improved performance during writing of information. In one embodiment, the recording channel front-end circuit includes a voltage-type write driver coupled to the transmission line interconnect and operable to output a write driver signal to the transmission line interconnect and a receiver termination circuit coupling the transmission line interconnect to the write element. The receiver termination circuit may include an impedance matching network operable match a terminal impedance of the write element to be substantially equal to a characteristic impedance of the transmission line interconnect.
    Type: Grant
    Filed: December 28, 1999
    Date of Patent: March 12, 2002
    Assignee: International Business Machines Corp.
    Inventors: John T. Contreras, David Anthony Freitas, Klaassen Berend Klaassen
  • Patent number: 6130795
    Abstract: An apparatus and method for sensing and reporting connection integrity of a differential transmission line having proper parallel termination is constructed by generating an error signal which indicates that one or both differential input lines are open. The error signal is generated using a voltage comparator having a first and second input in which these inputs are coupled to the first and second ECL signal lines. The first and second input lines are also coupled to a supply voltage by a first and second dynamic impedance such that the input is pulled high when the signal lines are open. The comparator generates an error signal when the input voltages are greater than voltages normally seen on the signal lines indicating the presence of a open transmission line.
    Type: Grant
    Filed: May 5, 1998
    Date of Patent: October 10, 2000
    Assignee: International Business Machines Corporation
    Inventors: David Anthony Freitas, Kevin Roy Vannorsdel
  • Patent number: 5801896
    Abstract: Track information decoding circuitry of a data storage device servo control system decodes binary track information in a readback servo signal by detecting opposite polarity track information pulse pairs so as to produce a track information signal "one" bit if the presence of an opposite polarity pulse pair is detected and produce a track information signal "zero" bit in the absence of an opposite polarity pulse pair, wherein a one bit is produced only if there has been detected a second pulse of a readback signal pulse pair having a magnitude greater than a predetermined threshold value and having a correct polarity. The polarity of the last di-bit of the servo signal AGC field can be used to set the polarity in the pulse qualification process.
    Type: Grant
    Filed: June 5, 1997
    Date of Patent: September 1, 1998
    Assignee: International Business Machines Corporation
    Inventor: David Anthony Freitas
  • Patent number: 5793556
    Abstract: A channel circuit that receives an analog disk readback signal of a data storage disk drive includes a comparator string and a data channel binary decoder that together comprise what is commonly referred to as a flash analog-to-digital (A/D) converter, which processes the data channel information of the readback signal. The servo information of the readback signal is provided to the comparator string of the data channel flash A/D converter, whose output then is provided to a servo burst binary decoder for decoding to produce the desired servo burst data. Thus, the servo information is digitized and decoded at the relatively high speed possible with a flash A/D converter, without requiring a comparator string in addition to what would otherwise be provided for the data channel application.
    Type: Grant
    Filed: October 19, 1994
    Date of Patent: August 11, 1998
    Assignee: International Business Machines Corporation
    Inventor: David Anthony Freitas